hw/char/virtio-console.c

   1 /*
   2  * Virtio Console and Generic Serial Port Devices
   3  *
   4  * Copyright Red Hat, Inc. 2009, 2010
   5  *
   6  * Authors:
   7  *  Amit Shah <amit.shah@redhat.com>
   8  *
   9  * This work is licensed under the terms of the GNU GPL, version 2.  See
  10  * the COPYING file in the top-level directory.
  11  */
  12
  13 #include "qemu/osdep.h"
  14 #include "chardev/char-fe.h"
  15 #include "qemu/error-report.h"
  16 #include "qemu/module.h"
  17 #include "trace.h"
  18 #include "hw/qdev-properties.h"
  19 #include "hw/virtio/virtio-serial.h"
  20 #include "qapi/error.h"
  21 #include "qapi/qapi-events-char.h"
  22
  23 #define TYPE_VIRTIO_CONSOLE_SERIAL_PORT "virtserialport"
  24 #define VIRTIO_CONSOLE(obj) \
  25     OBJECT_CHECK(VirtConsole, (obj), TYPE_VIRTIO_CONSOLE_SERIAL_PORT)
  26
  27 typedef struct VirtConsole {
  28     VirtIOSerialPort parent_obj;
  29
  30     CharBackend chr;
  31     guint watch;
  32 } VirtConsole;
  33
  34 /*
  35  * Callback function that's called from chardevs when backend becomes
  36  * writable.
  37  */
  38 static gboolean chr_write_unblocked(GIOChannel *chan, GIOCondition cond,
  39                                     void *opaque)
  40 {
  41     VirtConsole *vcon = opaque;
  42
  43     vcon->watch = 0;
  44     virtio_serial_throttle_port(VIRTIO_SERIAL_PORT(vcon), false);
  45     return FALSE;
  46 }
  47
  48 /* Callback function that's called when the guest sends us data */
  49 static ssize_t flush_buf(VirtIOSerialPort *port,
  50                          const uint8_t *buf, ssize_t len)
  51 {
  52     VirtConsole *vcon = VIRTIO_CONSOLE(port);
  53     ssize_t ret;
  54
  55     if (!qemu_chr_fe_backend_connected(&vcon->chr)) {
  56         /* If there's no backend, we can just say we consumed all data. */
  57         return len;
  58     }
  59
  60     ret = qemu_chr_fe_write(&vcon->chr, buf, len);
  61     trace_virtio_console_flush_buf(port->id, len, ret);
  62
  63     if (ret < len) {
  64         VirtIOSerialPortClass *k = VIRTIO_SERIAL_PORT_GET_CLASS(port);
  65
  66         /*
  67          * Ideally we'd get a better error code than just -1, but
  68          * that's what the chardev interface gives us right now.  If
  69          * we had a finer-grained message, like -EPIPE, we could close
  70          * this connection.
  71          */
  72         if (ret < 0)
  73             ret = 0;
  74
  75         /* XXX we should be queuing data to send later for the
  76          * console devices too rather than silently dropping
  77          * console data on EAGAIN. The Linux virtio-console
  78          * hvc driver though does sends with spinlocks held,
  79          * so if we enable throttling that'll stall the entire
  80          * guest kernel, not merely the process writing to the
  81          * console.
  82          *
  83          * While we could queue data for later write without
  84          * enabling throttling, this would result in the guest
  85          * being able to trigger arbitrary memory usage in QEMU
  86          * buffering data for later writes.
  87          *
  88          * So fixing this problem likely requires fixing the
  89          * Linux virtio-console hvc driver to not hold spinlocks
  90          * while writing, and instead merely block the process
  91          * that's writing. QEMU would then need some way to detect
  92          * if the guest had the fixed driver too, before we can
  93          * use throttling on host side.
  94          */
  95         if (!k->is_console) {
  96             virtio_serial_throttle_port(port, true);
  97             if (!vcon->watch) {
  98                 vcon->watch = qemu_chr_fe_add_watch(&vcon->chr,
  99                                                     G_IO_OUT|G_IO_HUP,
 100                                                     chr_write_unblocked, vcon);
 101             }
 102         }
 103     }
 104     return ret;
 105 }
 106
 107 /* Callback function that's called when the guest opens/closes the port */
 108 static void set_guest_connected(VirtIOSerialPort *port, int guest_connected)
 109 {
 110     VirtConsole *vcon = VIRTIO_CONSOLE(port);
 111     DeviceState *dev = DEVICE(port);
 112     VirtIOSerialPortClass *k = VIRTIO_SERIAL_PORT_GET_CLASS(port);
 113
 114     if (!k->is_console) {
 115         qemu_chr_fe_set_open(&vcon->chr, guest_connected);
 116     }
 117
 118     if (dev->id) {
 119         qapi_event_send_vserport_change(dev->id, guest_connected);
 120     }
 121 }
 122
 123 static void guest_writable(VirtIOSerialPort *port)
 124 {
 125     VirtConsole *vcon = VIRTIO_CONSOLE(port);
 126
 127     qemu_chr_fe_accept_input(&vcon->chr);
 128 }
 129
 130 /* Readiness of the guest to accept data on a port */
 131 static int chr_can_read(void *opaque)
 132 {
 133     VirtConsole *vcon = opaque;
 134
 135     return virtio_serial_guest_ready(VIRTIO_SERIAL_PORT(vcon));
 136 }
 137
 138 /* Send data from a char device over to the guest */
 139 static void chr_read(void *opaque, const uint8_t *buf, int size)
 140 {
 141     VirtConsole *vcon = opaque;
 142     VirtIOSerialPort *port = VIRTIO_SERIAL_PORT(vcon);
 143
 144     trace_virtio_console_chr_read(port->id, size);
 145     virtio_serial_write(port, buf, size);
 146 }
 147
 148 static void chr_event(void *opaque, int event)
 149 {
 150     VirtConsole *vcon = opaque;
 151     VirtIOSerialPort *port = VIRTIO_SERIAL_PORT(vcon);
 152
 153     trace_virtio_console_chr_event(port->id, event);
 154     switch (event) {
 155     case CHR_EVENT_OPENED:
 156         virtio_serial_open(port);
 157         break;
 158     case CHR_EVENT_CLOSED:
 159         if (vcon->watch) {
 160             g_source_remove(vcon->watch);
 161             vcon->watch = 0;
 162         }
 163         virtio_serial_close(port);
 164         break;
 165     }
 166 }
 167
 168 static int chr_be_change(void *opaque)
 169 {
 170     VirtConsole *vcon = opaque;
 171     VirtIOSerialPort *port = VIRTIO_SERIAL_PORT(vcon);
 172     VirtIOSerialPortClass *k = VIRTIO_SERIAL_PORT_GET_CLASS(port);
 173
 174     if (k->is_console) {
 175         qemu_chr_fe_set_handlers(&vcon->chr, chr_can_read, chr_read,
 176                                  NULL, chr_be_change, vcon, NULL, true);
 177     } else {
 178         qemu_chr_fe_set_handlers(&vcon->chr, chr_can_read, chr_read,
 179                                  chr_event, chr_be_change, vcon, NULL, false);
 180     }
 181
 182     if (vcon->watch) {
 183         g_source_remove(vcon->watch);
 184         vcon->watch = qemu_chr_fe_add_watch(&vcon->chr,
 185                                             G_IO_OUT | G_IO_HUP,
 186                                             chr_write_unblocked, vcon);
 187     }
 188
 189     return 0;
 190 }
 191
 192 static void virtconsole_enable_backend(VirtIOSerialPort *port, bool enable)
 193 {
 194     VirtConsole *vcon = VIRTIO_CONSOLE(port);
 195
 196     if (!qemu_chr_fe_backend_connected(&vcon->chr)) {
 197         return;
 198     }
 199
 200     if (enable) {
 201         VirtIOSerialPortClass *k = VIRTIO_SERIAL_PORT_GET_CLASS(port);
 202
 203         qemu_chr_fe_set_handlers(&vcon->chr, chr_can_read, chr_read,
 204                                  k->is_console ? NULL : chr_event,
 205                                  chr_be_change, vcon, NULL, false);
 206     } else {
 207         qemu_chr_fe_set_handlers(&vcon->chr, NULL, NULL, NULL,
 208                                  NULL, NULL, NULL, false);
 209     }
 210 }
 211
 212 static void virtconsole_realize(DeviceState *dev, Error **errp)
 213 {
 214     VirtIOSerialPort *port = VIRTIO_SERIAL_PORT(dev);
 215     VirtConsole *vcon = VIRTIO_CONSOLE(dev);
 216     VirtIOSerialPortClass *k = VIRTIO_SERIAL_PORT_GET_CLASS(dev);
 217
 218     if (port->id == 0 && !k->is_console) {
 219         error_setg(errp, "Port number 0 on virtio-serial devices reserved "
 220                    "for virtconsole devices for backward compatibility.");
 221         return;
 222     }
 223
 224     if (qemu_chr_fe_backend_connected(&vcon->chr)) {
 225         /*
 226          * For consoles we don't block guest data transfer just
 227          * because nothing is connected - we'll just let it go
 228          * whetherever the chardev wants - /dev/null probably.
 229          *
 230          * For serial ports we need 100% reliable data transfer
 231          * so we use the opened/closed signals from chardev to
 232          * trigger open/close of the device
 233          */
 234         if (k->is_console) {
 235             qemu_chr_fe_set_handlers(&vcon->chr, chr_can_read, chr_read,
 236                                      NULL, chr_be_change,
 237                                      vcon, NULL, true);
 238             virtio_serial_open(port);
 239         } else {
 240             qemu_chr_fe_set_handlers(&vcon->chr, chr_can_read, chr_read,
 241                                      chr_event, chr_be_change,
 242                                      vcon, NULL, false);
 243         }
 244     }
 245 }
 246
 247 static void virtconsole_unrealize(DeviceState *dev, Error **errp)
 248 {
 249     VirtConsole *vcon = VIRTIO_CONSOLE(dev);
 250
 251     if (vcon->watch) {
 252         g_source_remove(vcon->watch);
 253     }
 254 }
 255
 256 static void virtconsole_class_init(ObjectClass *klass, void *data)
 257 {
 258     VirtIOSerialPortClass *k = VIRTIO_SERIAL_PORT_CLASS(klass);
 259
 260     k->is_console = true;
 261 }
 262
 263 static const TypeInfo virtconsole_info = {
 264     .name          = "virtconsole",
 265     .parent        = TYPE_VIRTIO_CONSOLE_SERIAL_PORT,
 266     .class_init    = virtconsole_class_init,
 267 };
 268
 269 static Property virtserialport_properties[] = {
 270     DEFINE_PROP_CHR("chardev", VirtConsole, chr),
 271     DEFINE_PROP_END_OF_LIST(),
 272 };
 273
 274 static void virtserialport_class_init(ObjectClass *klass, void *data)
 275 {
 276     DeviceClass *dc = DEVICE_CLASS(klass);
 277     VirtIOSerialPortClass *k = VIRTIO_SERIAL_PORT_CLASS(klass);
 278
 279     k->realize = virtconsole_realize;
 280     k->unrealize = virtconsole_unrealize;
 281     k->have_data = flush_buf;
 282     k->set_guest_connected = set_guest_connected;
 283     k->enable_backend = virtconsole_enable_backend;
 284     k->guest_writable = guest_writable;
 285     dc->props = virtserialport_properties;
 286 }
 287
 288 static const TypeInfo virtserialport_info = {
 289     .name          = TYPE_VIRTIO_CONSOLE_SERIAL_PORT,
 290     .parent        = TYPE_VIRTIO_SERIAL_PORT,
 291     .instance_size = sizeof(VirtConsole),
 292     .class_init    = virtserialport_class_init,
 293 };
 294
 295 static void virtconsole_register_types(void)
 296 {
 297     type_register_static(&virtserialport_info);
 298     type_register_static(&virtconsole_info);
 299 }
 300
 301 type_init(virtconsole_register_types)